Terminal device, telecommunications apparatus and methods

ABSTRACT

A method of transmitting data by a terminal device operating in a wireless communications system comprising a non-terrestrial network access node and the terminal device, comprises the terminal device receiving an indication of an initial value of a set of one or more communications parameters for transmitting radio signals carrying the data, and modelling a state of a communications channel from the terminal device to a non-terrestrial network access node, in which a link adaptation procedure is used to select a revised value of the set of the one or more communications parameters with respect to the initial value of the set of the one or more communications parameters for the modelled channel state, and the method includes adapting the value of the set of the one or more communications parameters according to the revised value.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.17/277,294, filed Mar. 18, 2021, which is based on PCT filingPCT/EP2019/075292, filed Sep. 20, 2019, which claims priority to EP18197363.7, filed Sep. 27, 2018, the entire contents of each areincorporated herein by reference.

BACKGROUND Field

The present disclosure relates to telecommunications apparatus, terminaldevices configured to communicate in co-operation with atelecommunications and methods. In some embodiments thetelecommunications system may include a non-terrestrial network accessnode.

Description of Related Art

The “background” description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description which may nototherwise qualify as prior art at the time of filing, are neitherexpressly or impliedly admitted as prior art against the presentinvention.

Third and fourth generation mobile telecommunication systems, such asthose based on the 3GPP defined UMTS and Long Term Evolution (LTE)architecture, are able to support more sophisticated services thansimple voice and messaging services offered by previous generations ofmobile telecommunication systems. For example, with the improved radiointerface and enhanced data rates provided by LTE systems, a user isable to enjoy high data rate applications such as mobile video streamingand mobile video conferencing that would previously only have beenavailable via a fixed line data connection. The demand to deploy suchnetworks is therefore strong and the coverage area of these networks,i.e. geographic locations where access to the networks is possible, maybe expected to increase ever more rapidly.

In view of this there is expected to be a desire for future wirelesscommunications networks, for example those which may be referred to as5G using a new radio (NR) system/new radio access technology (RAT)systems, as well as future iterations/releases of existing systems, toefficiently support a wide range of devices associated with differentoperating characteristics in areas that may be difficult to service fromconventional terrestrial networks, for example in the open sea.

One area of current interest in this regard includes so-called“non-terrestrial networks”, or NTN for short. The 3GPP has proposed inRelease 15 of the 3GPP specifications to develop technologies forproviding coverage by means of one or more antennas mounted on anairborne or space-borne vehicle [1].

Non-terrestrial networks may provide service in areas that cannot becovered by terrestrial cellular networks (i.e. those where coveragecannot be provided by means of land-based antennas), such as isolated orremote areas, on board aircraft or ship) and/or may be used to provideenhanced service in areas that are also served by land-based networknodes. The expanded coverage that may be achieved by means ofnon-terrestrial networks may provide service continuity formachine-to-machine (M2M) or ‘internet of things’ (IoT) devices, or forpassengers on board moving platforms (e.g. passenger vehicles such asaircraft, ships, high speed trains, or buses). Other benefits may arisefrom the use of non-terrestrial networks for providingmulticast/broadcast resources for data delivery.

The use of different types of network infrastructure equipment, such asNTN nodes and requirements for coverage enhancement give rise to newchallenges for handling communications in wireless telecommunicationssystems that need to be addressed.

SUMMARY

Respective aspects and features of the present disclosure are defined inthe appended claims.

Embodiments of the present technique can for example provide a method oftransmitting data by a terminal device operating in a wirelesscommunications system. The wireless communications system may comprise anon-terrestrial network access node and the terminal device. The methodcomprises the terminal device receiving an indication of an initialvalue of a set of one or more communications parameters for transmittingradio signals carrying the data, modelling a state of a communicationschannel from the terminal device to a receiver of the radio signals, inwhich a link adaptation procedure is used to select a revised value ofthe set of the one or more communications parameters with respect to theinitial value of the set of the one or more communications parametersfor the modelled channel state, and adapting the value of the set of theone or more communications parameters according to the revised value.The method then includes transmitting radio signals representing thedata using the set of the one or more communications parameters. Themethod may also include determining whether the revised communicationsparameters have changed with respect to the initial parameters, and soonly revising the communications parameters if these have changed withrespect to the initial value.

Embodiments of the present technique can provide an arrangement in whichlink adaptation is performed without a feedback of a channel state ofthe communications channel from a receiver of uplink data, therebysaving on communications resources required for a feedback channel orindeed making link adaptation possible where a round trip delay makesproviding feedback of a channel state in practical. Embodiments may alsobe provided correspondingly for down link transmissions. Embodiments canfind application with non-terrestrial network access nodes which aretypically deployed at greater distances requiring greater transmissionpropagation times inhibiting feedback or reference signals to betransmitted and received or for examples in which no communicationsresources are available for transmitting channel state informationmeasured at a receiver.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary, but are notrestrictive, of the present technology. The described embodiments,together with further advantages, will be best understood by referenceto the following detailed description taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings wherein likereference numerals designate identical or corresponding parts throughoutthe several views, and wherein:

FIG. 1 schematically represents some aspects of a LTE-type wirelesstelecommunication system which may be configured to operate inaccordance with certain embodiments of the present disclosure;

FIG. 2 schematically represents some aspects of a new radio accesstechnology (RAT) wireless telecommunications system which may beconfigured to operate in accordance with certain embodiments of thepresent disclosure;

FIG. 3 schematically represents some aspects of a wirelesstelecommunication system in accordance with certain embodiments of thepresent disclosure; and

FIG. 4 is a flow diagram providing a first illustration of an embodimentof the present technique; and

FIG. 5 is a flow diagram providing a first illustration of an embodimentof the present technique.

DESCRIPTION OF EXAMPLE EMBODIMENTS

FIG. 1 provides a schematic diagram illustrating some basicfunctionality of a mobile telecommunications network/system 100operating generally in accordance with LTE principles, but which mayalso support other radio access technologies, and which may be adaptedto implement embodiments of the disclosure as described herein. Variouselements of FIG. 1 and certain aspects of their respective modes ofoperation are well-known and defined in the relevant standardsadministered by the 3GPP® body and associated proposals, and alsodescribed in many books on the subject, for example, Holma H. andToskala A [2]. It will be appreciated that operational aspects of thetelecommunications networks discussed herein which are not specificallydescribed (for example in relation to specific communication protocolsand physical channels for communicating between different elements) maybe implemented in accordance with any known techniques, for exampleaccording to the relevant standards and known proposed modifications andadditions to the relevant standards.

The network 100 includes a plurality of base stations 101 connected to acore network 102. Each base station provides a coverage area 103 (i.e. acell/spot-beam) within which data can be communicated to and fromterminal devices 104. In accordance with NTN proposals one or more basestations may be non-terrestrial, e.g. satellite based. In this regard itwill be appreciated that satellite based means that the base station maybe either physically on board of a non-terrestrial platform such as asatellite, or transmissions between the base station and the UEs transitthrough a non-terrestrial platform such as a satellite. Data istransmitted from base stations 101 to terminal devices 104 within theirrespective coverage areas 103 via a radio downlink. The coverage areamay be referred to as a cell, and in the case of an NTN basestation/radio access node, the coverage area may also be referred to asa spot-beam (a single NTN platform may support multiple spot-beams) Datais transmitted from terminal devices 104 to the base stations 101 via aradio uplink. The core network 102 routes data to and from the terminaldevices 104 via the respective base stations 101 and provides functionssuch as authentication, mobility management, charging and so on.Terminal devices may also be referred to as mobile stations, userequipment (UE), user terminal, mobile radio, communications device, andso forth. Base stations, which are an example of network infrastructureequipment/network access node, may also be referred to as transceiverstations/NodeBs/e-NodeBs, g-NodeBs and so forth, and as noted above inan NTN network one or more base stations may be satellite based. In thisregard different terminology is often associated with differentgenerations of wireless telecommunications systems for elementsproviding broadly comparable functionality. However, certain embodimentsof the disclosure may be equally implemented in different generations ofwireless telecommunications systems, and for simplicity certainterminology may be used regardless of the underlying networkarchitecture. That is to say, the use of a specific term in relation tocertain example implementations is not intended to indicate theseimplementations are limited to a certain generation of network that maybe most associated with that particular terminology.

FIG. 2 is a schematic diagram illustrating a network architecture for anew RAT wireless mobile telecommunications network/system 300 based onpreviously proposed approaches which may also be adapted to providefunctionality in accordance with embodiments of the disclosure describedherein, and which may again include one or more NTN components providingradio access through a non-terrestrial node. The new RAT network 300represented in FIG. 2 comprises a first communication cell 301 and asecond communication cell 302. Each communication cell 301, 302,comprises a controlling node (centralised unit) 321, 322 incommunication with a core network component 310 over a respective wiredor wireless link 351, 352. The respective controlling nodes 321, 322 arealso each in communication with a plurality of distributed units (radioaccess nodes/remote transmission and reception points (TRPs)) 311, 312in their respective cells. Again, these communications may be overrespective wired or wireless links. The distributed units 311, 312 areresponsible for providing the radio access interface for terminaldevices connected to the network, and as noted above some of these maybe non-terrestrial in a network having an NTN part. Each distributedunit 311, 312 has a coverage area (radio access footprint) 341, 342which together define the coverage of the respective communication cells301, 302. Each distributed unit 311, 312 includes transceiver circuitry311 a, 312 a for transmission and reception of wireless signals andprocessor circuitry 311 a, 311 b configured to control the respectivedistributed units 311, 312.

In terms of broad top-level functionality, the core network component310 of the telecommunications system represented in FIG. 2 may bebroadly considered to correspond with the core network 102 representedin FIG. 1 , and the respective controlling nodes 321, 322 and theirassociated distributed units/TRPs 311, 312 may be broadly considered toprovide functionality corresponding to base stations of FIG. 1 . Theterm network infrastructure equipment/access node may be used toencompass these elements and more conventional base station typeelements of wireless telecommunications systems. Depending on theapplication at hand the responsibility for scheduling transmissionswhich are scheduled on the radio interface between the respectivedistributed units and the terminal devices may lie with the controllingnode/centralised unit and/or the distributed units/TRPs.

A terminal device 400 is represented in FIG. 2 within the coverage areaof the first communication cell 301. This terminal device 400 may thusexchange signalling with the first controlling node 321 in the firstcommunication cell via one of the distributed units 311 associated withthe first communication cell 301. In some cases communications for agiven terminal device are routed through only one of the distributedunits, but it will be appreciated in some other implementationscommunications associated with a given terminal device may be routedthrough more than one distributed unit, for example in a soft handoverscenario and other scenarios. The particular distributed unit(s) throughwhich a terminal device is currently connected through to the associatedcontrolling node may be referred to as active distributed units for theterminal device. Thus the active subset of distributed units for aterminal device may comprise one or more than one distributed unit(TRP). The controlling node 321 is responsible for determining which ofthe distributed units 311 spanning the first communication cell 301 isresponsible for radio communications with the terminal device 400 at anygiven time (i.e. which of the distributed units are currently activedistributed units for the terminal device). Typically this will be basedon measurements of radio channel conditions between the terminal device400 and respective ones of the distributed units 311. In this regard, itwill be appreciated the subset of the distributed units in a cell whichare currently active for a terminal device will depend, at least inpart, on the location of the terminal device within the cell (since thiscontributes significantly to the radio channel conditions that existbetween the terminal device and respective ones of the distributedunits).

In at least some implementations the involvement of the distributedunits in routing communications from the terminal device to acontrolling node (controlling unit) is transparent to the terminaldevice 400. That is to say, in some cases the terminal device may not beaware of which distributed unit is responsible for routingcommunications between the terminal device 400 and the controlling node321 of the communication cell 301 in which the terminal device iscurrently operating. In such cases, as far as the terminal device isconcerned, it simply transmits uplink data to the controlling node 321and receives downlink data from the controlling node 321 and theterminal device has no awareness of the involvement of the distributedunits 311. However, in other embodiments, a terminal device may be awareof which distributed unit(s) are involved in its communications.Switching and scheduling of the one or more distributed units may bedone at the network controlling node based on measurements by thedistributed units of the terminal device uplink signal or measurementstaken by the terminal device and reported to the controlling node viaone or more distributed units

In the example of FIG. 2 , two communication cells 301, 302 and oneterminal device 400 are shown for simplicity, but it will of course beappreciated that in practice the system may comprise a larger number ofcommunication cells (each supported by a respective controlling node andplurality of distributed units) serving a larger number of terminaldevices.

It will further be appreciated that FIG. 2 represents merely one exampleof a proposed architecture for a new RAT telecommunications system inwhich approaches in accordance with the principles described herein maybe adopted, and the functionality disclosed herein may also be appliedin respect of wireless telecommunications systems having differentarchitectures.

Thus certain embodiments of the disclosure as discussed herein may beimplemented in wireless telecommunication systems/networks according tovarious different architectures, such as the example architectures shownin FIGS. 1 and 2 . It will thus be appreciated the specific wirelesstelecommunications architecture in any given implementation is not ofprimary significance to the principles described herein. In this regard,certain embodiments of the disclosure may be described generally in thecontext of communications between network infrastructureequipment/access nodes, including NTN infrastructure equipment/accessnodes, and a terminal device, wherein the specific nature of the networkinfrastructure equipment/access node and the terminal device will dependon the network infrastructure for the implementation at hand. Forexample, in some scenarios the network infrastructure equipment/accessnode may comprise a base station, such as an LTE-type base station 101as shown in FIG. 1 which is adapted to provide functionality inaccordance with the principles described herein, and in other examplesthe network infrastructure equipment may comprise a controlunit/controlling node 321, 322 and/or a TRP 311, 312 of the kind shownin FIG. 2 which is adapted to provide functionality in accordance withthe principles described herein.

FIG. 3 schematically shows some aspects of a telecommunications system500 configured to support communications between a terminal device 508and network access nodes 504, 506 in accordance with certain embodimentsof the disclosure. One network access node is a terrestrial networkaccess node 506 and one network access node is a non-terrestrial networkaccess node 504, in this example an orbital satellite based terrestrialnetwork access node. Many aspects of the operation of thetelecommunications system/network 500 are known and understood and arenot described here in detail in the interest of brevity. Aspects of thearchitecture and operation of the telecommunications system 500 whichare not specifically described herein may be implemented in accordancewith any previously proposed techniques, for example according tocurrent 3GPP standards and other proposals for operating wirelesstelecommunications systems/networks. The network access nodes 504, 506may, for convenience, sometimes be referred to herein as base stations504, 506, it being understood this term is used for simplicity and isnot intended to imply any network access node should conform to anyspecific network architecture or should be terrestrial, but on thecontrary, may correspond with any network infrastructureequipment/network access node that may be configured to providefunctionality as described herein. In that sense it will appreciated thespecific network architecture in which embodiments of the disclosure maybe implemented is not of primary significance to the principlesdescribed herein.

The telecommunications system 500 comprises a core network part 502coupled to a radio network part. The radio network part comprises theradio network access nodes 504, 506 and the terminal device 508. It willof course be appreciated that in practice the radio network part maycomprise a more than two network access nodes serving multiple terminaldevices across various communication cells/spot-beams. However, only twonetwork access nodes and one terminal device are shown in FIG. 3 in theinterests of simplicity.

The terminal device 508 is arranged to communicate data to and from thenetwork access nodes (base stations/transceiver stations) 504, 506according to coverage. For the example shown in FIG. 3 it is assumed theterminal device 508 is currently within the coverage area/spot-beam 510of the NTN radio access node 504. Typically the terminal device will beoperable to connect to (i.e. be able to exchange user plane data with)one network infrastructure element at a time, and so as the terminaldevice moves around the network it may move in and out of coverage ofthe different network access nodes comprising the network. A particularissue with NTN radio access nodes is that the coverage area/spot-beamcan itself move rapidly across the earth's surface so that a terminaldevice may move in and out of the coverage area of an NTN radio accessnodes relatively quickly, even when the terminal device itself may bestationary.

The network access nodes 504, 506, are communicatively connected to acore network part which is arranged to perform routing and management ofmobile communications services to the terminal devices in thetelecommunications system 500 via the network access nodes 504, 506. Theconnection from the NTN network access nodes 504 to the core network 502is wireless while the connection from the terrestrial network accessnode 506 to the core network 502 may be wired or wireless. In order tomaintain mobility management and connectivity, the core network part 502also includes a mobility management entity, MME, 520 which manages theservice, connections with terminal devices operating in thecommunications system. As noted above, the operation of the variouselements of the communications system 500 shown in FIG. 3 may be inaccordance with known techniques apart from where modified to providefunctionality in accordance with embodiments of the present disclosureas discussed herein.

The terminal device 508 is adapted to support operations in accordancewith embodiments of the present disclosure when communicating with thenetwork access nodes 504, 506. The terminal device 508 comprisestransmitter circuitry 540 for transmission of wireless signals, receivercircuitry 542 and controller or processor circuitry 544 (which may alsobe referred to as a processor/processor unit) configured to control theterminal device 508. The processor circuitry 544 may comprise varioussub-units/sub-circuits for providing desired functionality as explainedfurther herein. These sub-units may be implemented as discrete hardwareelements or as appropriately configured functions of the processorcircuitry. Thus the processor circuitry 544 may comprise circuitry whichis suitably configured/programmed to provide the desired functionalitydescribed herein using conventional programming/configuration techniquesfor equipment in wireless telecommunications systems. The transmitterand receiver circuitry 340, 542 and the processor circuitry 544 areschematically shown in FIG. 3 as separate elements for ease ofrepresentation. However, it will be appreciated that the functionalityof these circuitry elements can be provided in various different ways,for example using one or more suitably programmed programmablecomputer(s), or one or more suitably configured application-specificintegrated circuit(s)/circuitry/chip(s)/chipset(s). It will beappreciated the terminal device 508 will in general comprise variousother elements associated with its operating functionality, for examplea power source, user interface, and so forth, but these are not shown inFIG. 3 in the interests of simplicity.

The network access nodes 504, 506 each comprises transmitter circuitry530, 550 (which may also be referred to as a transceiver/transceiverunit) for transmission of wireless signals, receiver circuitry 532, 552for receiving wireless signals and controller or processor circuitry534, 554 (which may also be referred to as a processor/processor unit)configured to control the respective network access nodes 504, 506 tooperate in accordance with embodiments of the present disclosure asdescribed herein. Thus, the processor circuitry 534, 554 for eachnetwork access node 504, 506 may comprise circuitry which is suitablyconfigured/programmed to provide the desired functionality describedherein using conventional programming/configuration techniques forequipment in wireless telecommunications systems. For each networkaccess nodes 504, 506 the transmitter and receiver circuitry 530, 532,550, 552 and the processor circuitry 534, 554 are schematically shown inFIG. 3 as separate elements for ease of representation. However, it willbe appreciated that the functionality of these circuitry elements can beprovided in various different ways, for example using one or moresuitably programmed programmable computer(s), or one or more suitablyconfigured application-specific integratedcircuit(s)/circuitry/chip(s)/chipset(s). It will be appreciated thateach of the network access nodes 504, 506 will in general comprisevarious other elements associated with its operating functionality, suchas a scheduler. For example, although not shown in FIG. 3 forsimplicity, the processor circuitry 534, 554 may comprise schedulingcircuitry, that is to say the processor circuitry 534, 554 may beconfigured/programmed to provide the scheduling function for the networkaccess node.

Thus, some networks may include non-terrestrial network (NTN) partswhich may either be fully integrated with a terrestrial network, as inthe example of FIG. 3 , or may operate as a stand-alonenon-terrestrial-network.

The NTN network may be associated with a number of different platformshaving different characteristics. Some proposals for NTN are indicatedin the following table:

Altitude Beam footprint Platform range (km) Orbit Shape diameter (km)Low-Earth Orbit (LEO) 300-1500 Circular around Earth 100-500  satelliteMedium-Earth Orbit (MEO) 7000-25000 100-500  satellite GeostationaryEarth Orbit 35786 Notionally stationary at 200-1000 (GEO) satellitefixed position in terms of UAS (unmanned aircraft 8-50 elevation/azimuthwith  5-200 system) platform (including (20 HAPS) respect to a givenlocation HAPS - high altitude pseudo- on Earth satellite). May also bereferred to as a Drone platform. High Elliptical Orbit (HEO)  400-50000Elliptical around Earth 200-1000 satellite

In terms of mobility management, NTNs based on GEO-satellite andUAS/HAPS platforms are similar to terrestrial networks in that the cells(base stations) are notionally stationary and it is movement of terminaldevices relative to the cells that gives rise to mobility within thenetwork. This means mobility management procedures for such NTN networkaccess nodes can, in essence, be implemented in the same manner as forterrestrial networks (potentially taking account of differences insignal propagation time as appropriate).

However for non-geostationary NTN platforms, e.g. LEO, MEO and HEOsatellite platforms, the satellite (i.e. the base station/NTN radioaccess node) moves with respect to the earth, and so itscoverage/spot-beam(s) also moves across the surface of the earth,typically relatively quickly. This means that whereas for a stationarycell (e.g. terrestrial base station or GEO satellite base station) theterminal device's movement relative to earth is what gives rise tomobility (ignoring changing radio channel conditions), fornon-geostationary NTN platforms, terminal device mobility within thenetwork is typically exceeded by the movement of the basestation/satellite itself since the coverage footprint ofnon-geostationary NTN platforms will typically be moving across theearth significantly faster than terminal devices.

Due to the movement of non-geostationary based NTN platform spot-beamfootprints across the earth, ubiquitous coverage may be provided byconstellations of satellites. Thus for a given location of a terminaldevice on the earth surface, as one satellite moves along its orbit, thelocation may be illuminated by a spot-beam of the satellite for a timeuntil that spot-beam footprint moves away from that location. Then thenext spot-beam, possibly from the same satellite, takes over coverage(illumination) of the location until its illumination in turn driftsaway from the location, and so on. Thus different spot-beams fromdifferent satellites provide coverage for a given location on the earthat different times.

LEO satellites at the highest orbital altitude in the table above mighthave an orbital speed of around 7 km/s and a spot-beam coverage ofaround 500 km. This means the satellite may move a linear distancecorresponding to the diameter of its spot-beam footprint in little morethan a minute (around 70 seconds). This means even a stationary terminaldevice may need to be handed over from one spot-beam 510, 512, 514 tothe next every minute or so for LEO satellites at the highest orbitalaltitude, and potentially more often still for lower altitude LEOsatellites which will move faster and typically have smaller diameterspot-beams.

As is well understood, wireless telecommunications networks may supportdifferent Radio Resource Control (RRC) modes for terminal devices,typically including: (i) RRC idle mode (RRC_IDLE); and (ii) RRCconnected mode (RRC_CONNECTED). A terminal device typically transmitsdata whilst in RRC connected mode. The RRC idle mode, on the other hand,is used for terminal devices which are registered to the network(EMM-REGISTERED), but not currently in active communication (ECM-IDLE).Thus, generally speaking, in RRC connected mode a terminal device isconnected to a radio network access node (e.g. base station, which maybe a non-terrestrial radio access node in a NTN) in the sense of beingable to exchange user plane data with the radio network access node.Conversely, in RRC idle mode a terminal device is not connected to aradio network access node in the sense of not being able to communicateuser plane data using the radio network access node. The RRC connectionsetup procedure of going from RRC idle mode to RRC connected mode may bereferred to as connecting to a cell/base station and entails theterminal device undertaking a RACH (random access channel) procedure,security activation procedure, RRC connection establishment procedureetc., which takes time to complete and consumes transmission resourcesin the network and power by the terminal device. In addition to theseidle and connected modes there are also proposals for other RRC modes,such as the so-called RRC_INACTIVE mode. A terminal device inRRC_INACTIVE mode is one which is not in an active RRC connected modewith the radio access network (RAN), but is considered to be connectedfrom a CN (core network) point of view, so that data can be sent withoutCN-level paging, but with paging performed instead at the RAN level, tocause/trigger the terminal device to resume RRC connection (e.g. enteran RRC connected mode) if necessary.

An advantage of the non-connected modes (RRC_IDLE and RRC_INACTIVE), isthat they can be used to help a terminal device save power, but theterminal devices may not be able to take full advantage of this if itneeds to transition to connected mode to transmit a location report toofrequently.

As noted above, for a NGSO non-geostationary orbit) platform in an NTN,the movement that dominates the need for mobility management is expectedto be that of the satellite rather than the terminal devices. That is tosay, it may be expected a terminal device is relatively stationary whencompared to the movement of spot-beams/cells of the satellites providingthe terminal device with coverage. For example, a proposal requirementfor NR telecommunication systems is to support a terminal device speedof up to 500 km/h (around 0.14 km/s), which is significantly less thanthe orbital speed of LEO satellites which is typically more than 7 km/s.

It is known generally that mobile communications systems provide anarrangement for adapting the signal coding and modulation of transmitterand receiver chain of circuits for communicating data in accordance withdynamically changing radio conditions. Such techniques, which arereferred to as link adaptation, typically involve adapting, for example,a size of a modulation scheme used to map the data for transmission onto carriers/sub-carriers (mQAM etc) as well as a coding rate of an errorcorrection encoding used to transmit and receive the data to improveintegrity with respect to communications resources consumed. In similarsystems, link adaptation adapts communications parameters of thetransmitted data in accordance with both radio propagation conditionsand a currently experienced interference from other cells transmittingon the same frequency and time. Link adaptation is performed in order toimprove an efficiency with which radio communications resources are usedwithin mobile communications systems.

Link adaptation also facilitates support of varying traffic demandswhilst taking UE mobility into account. In order to make link adaptationmost effective, a minimal response time in respect of the access controlfunctionality is required in order to perform the link adaptation withrespect to the dynamically changing communications conditions. Insimilar systems access control is typically located in a base stationsuch as a g-NodeB which is relatively close to the UE compared with anNTN base station. Moreover, with terrestrial systems coordinationbetween gNBs is possible through the XN interface (an interface betweengNB's) or via a central entity. For satellite systems however, accesscontrol is mostly located at a satellite base station, gateway or hublevel for which feedback required for link adaptation takes a longertime because of the propagation delay. This may prevent optimal or atleast an effective response time for access control and link adaptation.This is because the round trip delay for communications for satellitebase stations is typically much longer than those for conventionalterrestrial radio base stations. For this reason pre-grant ofcommunications resources, semi-persistent scheduling of communicationsresources to UE's and/or grant free access schemes can provide anadvantage in which there is a reduced requirement for an exchange ofsignalling messages such as access requests and resource allocationresponses to allow UEs to access communications resources.

In 3GPP release 15 standard relating to new radio or 5G, provides forsemi-persistent scheduling of downlink resources. The uplink isconfigured differently but semi-persistent scheduling of uplinkresources is supported for static scheduling grant parameters. Staticparameter configuration in which the communications parameters for thetransmitter and receiver chain are established on a fixed basis isreasonable for conventional (terrestrial) communications because a pathloss of the radio communications path or the channel quality typicallydoes not vary rapidly. However as indicated above for low orbitsatellites, a satellite may move 450 km in its orbit during 1 minute.With a low earth orbit satellite altitude of 600 km a difference inpropagation distance over a single minute is therefore significant. As aresult a propagation path loss as well as other radio conditions maychange significantly during a communications session.

As indicated above, because of the changing propagation conditions andradio communication conditions some form of link adaptation isappropriate in order to communicate data efficiently from a UE to asatellite base station as well as from the satellite base station to theUE. Conventionally link adaptation is based on performing RRC signallingin order to establish a radio bearer between the UE and the satellitebase station and then providing channel state information and linkquality information from the UE to the base station and vice versa inorder to adapt the communications parameters used for transmitting data.However, as a result of a delay in transmitting and receiving signalsbetween the UE and the satellite base station and the absence of channelstate information, which can be provided by a non-terrestrial node (NTN)base station, performing link adaption presents a technical problem.

Embodiments of the present technique provide an arrangement in which aUE is configured to predict a state of a radio communications channelfor transmitting signals from the UE to the NTN base station in order toperform an adaptation of communications parameters in accordance with alink adaptation procedure. According to the modelling performed by theUE, the UE predicts a required signal to interference and noise ratio(SINR) at the NTN base station using an internal model. The model mayrequire signal strength (pathloss) prediction, a prediction of noise andinterference as well as other parameters. Whilst this prediction mayhave some errors, other techniques can be used to compensate for theseerrors.

Embodiments of the present technique also provide an arrangement inwhich RRC parameters which are parameters of a radio bearer establishedbetween the UE and the NTN base station are arranged to changeinfrequently. As such, the RRC parameters may be semi-staticallyconfigured rather than dynamically configured based on an initial set ofcommunications parameters. The initial communications parameters areused by a model in the UE to generate adapted communications parameterswhich are changed dynamically from the initial set of parameters.

A further technical problem addressed by embodiments of the presenttechnique is to provide an arrangement in which detailed link adaptationparameters such as communications parameters are not transmitted fromthe UE to the NTN base station because a wireless access interfacebetween the UE and the NTN base station does not provide capacity fortransmitting these adapted communications parameters on an uplinkcontrol information indicator. Typical link adaptation parametersinclude a transport block size, a modulation scheme and a coding scheme.According to example embodiments, the adapted communications parametersare not fed back to the NTN base station on an uplink controlinformation (UCI) message on layer 1 as would be done conventionally fora terrestrial base station for example via a physical uplink controlchannel (PUCCH).

Embodiments of the present technique can provide an arrangement in whicha UE dynamically changes communications parameters with reduced RRCsignalling and without a real time base station providing feedback ondownlink control channel during uplink configured grant sessions.According to an example embodiment a UE receives an initial set ofparameters from a NTN base station and then internally generates a modeland predicts a channel state based for example on path loss between theUE and the NTN base station. The UE then estimates communicationsparameters with a predicted channel state and a required signal to noiseand interference ratio at the NTN base station. In one example, the NTNbase station may also generate the same model and therefore based on theinitial parameters which both the NTN base station and the UE know, theNTN base station may select communications parameters in accordance withlink adaption parameters in order to adapt the communications parametersof the transmitter and receiver chain from the UE to the NTN basestation. The UE then transmits data using the selected link adaptationparameters without necessarily providing an indication to the basestation of the communications parameters which have been selected. TheNTN base station detects the signal transmitted from the UE to estimatethe data using either a blind detection technique or using acorresponding prediction and link adaptation model which is beingperformed at the NTN base station.

Referring again to FIG. 3 , a UE 508 is shown to communicate with a NTNbase station 504 via one or more spot beams 510, 512, 514. A backhaulcommunication channel to the core network 502 is shown via acommunications interface 520. As already explained a conventionalterrestrial base station 506 is shown connected to the core network part502 via an interface 508.

Embodiments of the present technique can provide an arrangement forefficiently communicating data from a UE 508 to an NTN base station 504via one of the spot beams 510, 512, 514. As shown in FIG. 3 , the UE 508is currently located within a spot beam 510 within which radio signalsare transmitted and received between the UE 508 and the NTN base station504.

As explained above, on an uplink, the transmitter 540 of the UE 508 isconfigured to adapt communications parameters in accordance with a linkadaptation procedure to match the radio conditions experienced for radiocommunications within the beam 510 and a receiver 532 of the NTN basestation 504. Correspondingly, link adaptation can be performed by atransmitter 530 for radio signals transmitted from the NTN base station504 to the UE 508 and received by the receiver 542, the link adaptationprocedure adapting communications parameters for the transmitter 530 andthe receiver 542.

As will be appreciated the model of the channel state may include thelink adaptation procedure, because this may form an integral part ofassessing the channel, or the link adaptation procedure may form aseparate process from the model of the channel state which may thereforecommunicate an indication of the channel state via an interface.

The following embodiments of the present technique will be describedwith reference to the operation of the UE 508 in respect of uplink datatransmissions from the UE 508 to the NTN base stations 504. However itwill be appreciated that in other embodiments the present technique canbe applied equally to downlink communications that is performed by thecontroller 534 of the NTN base station 504 for transmission of data forreception by the UE 508 by the receiver 542.

An embodiment of the present technique is illustrated by the flowdiagram shown in FIG. 4 . It will be appreciated that the process stepsshown in FIG. 4 are performed generally by the controller 544 incombination with its control of the transmitter and the receiver 542.

As shown in FIG. 4 in first step S1 the NTN base station 504 transmitsan initial set of communications parameters with RRC signal which isperformed for example when a communications bearer is established by theradio link layer from the UE 508 to the NTN base station 504.

After receiving the initial parameters from the NTN base station, thecontroller 544 of the UE 508 generates a model for calculating a channelstate between the UE 508 and the NTN base station 504. In step S4, thecontroller 544 estimates a position of the NTN base station and predictsbased on its own position and therefore a relative distance between theUE 508 and the NTN base station 504 a path loss and result of radiocommunications based on the initial parameters provided in the RRCsignalling and other internal parameters. For example the RRC signallingmay establish an absolute radio frequency number used by the UE 508which can be used to predict the path loss between the UE 508 and theNTN base station 504 for the calculated distance. Thus in step S6 thecontroller 544 predicts a path loss between the UE and the NTN basestation 504. In step S8 the controller 544 predicts a noise andinterference with which signals will be received at the NTN base stationbased on the initial parameters and historical data such as a previousindication of interference at the NTN base station. In step S10 thecontroller 544 predicts a signal to interference and noise ratio at thereceiver 542 within the NTN base station 504 and in accordance with thepredicted path loss and the predicted signal to interference and noiseratio the controller selects new communications parameters in accordancewith a link adaptation procedure for the transmission of the uplinkdata.

In step S12 from the predicted communications parameters in accordancewith the link adaptation procedure, the controller 544 controls thetransmitter 540 to select a transport format comprising communicationsparameters and reapplies the communications parameters to transmit datato the NTN base station 504. The transmission of the data is representedby the arrow S14. The receiver 532 detects the radio signals transmittedon the uplink by the UE 508 and generates an estimate of the datacarried by those signals by decoding the data in accordance with thecommunications parameters used by the UE 508 which is without anexplicit indication of those communications parameters. This can beperformed by the controller 534 generating within the NTN base station504 a corresponding prediction of the model performed by the controller544 within the UE 508. Alternatively the receiver 532 can perform ablind detection of the data and blind decoding to recover an estimate ofthe data.

FIG. 5 provides a more detailed example of a general sequence inaccordance with a process of the link adaptation as represented in FIG.4 where the communications parameters required for link adaptation arepredicted. As shown in FIG. 5 , as a first step S20, the NTN basestation 504 transmits system information in accordance with aconventional arrangement which is detected by the UE 508. However inaccordance with example embodiments a pre-configuration ofcommunications parameters is provided with the system information whichcorresponds approximately to step S1 shown in FIG. 4 . In other examplesa sim card of the UE 508 may provide the preconfigured communicationsparameters or these may be provided in advance for example via aninternet connection.

In step S22, a communications session starts. The UE 508 then initiatesthe communications session by a request received from an applicationlayer programme. As shown by a message exchange S24, the UE establishesvia RRC signalling initial parameters for predicted grant of resourcesfor communications parameters which are identified in more detail below.The NTN base station 504 then replies with a message M2 providinginitial parameters for the predicted grant of uplink communicationsresources. It then follows a process of predicting the adaptation of thecommunications parameters as represented by FIG. 4 in steps S2-S12 inwhich the data is transmitted and received at the NTN base station 504as represented by a process at step S26. Accordingly during the processsteps S2-S12, the UE calculates the path loss and signal to interferenceand noise ratio with a model as explained above and generates adaptedcommunications parameters. The UE decides the communications parametersin accordance with a link adaptation procedure. Examples of thesecommunications parameters are shown below. The UE then transmits thedata using the selected communications parameters chosen using the linkadaptation procedure as represented by an arrow M4.

If the data is transmitted and received correctly and without error thenthe UE proceeds to transmit all of the data in its buffer using thenewly adapted communications parameters as represented by step S28. Inone example the decoding of the data present in the UEs buffer istriggered by an ACK transmitted from the network, such as that used aspart of an ARQ protocol. If however the UE decides that the sessionshould be suspended as a result of a predicted poor link quality and thesemi-persistent resources are temporally not used by the UE then amessage M6 is sent to the NTN base station 504. Correspondingly the UEmay send an activation of a semi-persistent session if a problem whichcaused the session to be suspended has been resolved using a message M8.Accordingly data is received again as represented by step S30. Once theUE 508 has transmitted all of the uplink data then the resources arereleased and the session ends as represented by step S32 and a releasemessage is sent to NTN base station 504 M10.

As explained above, in step S24 and the message exchange M1, M2 betweenthe NTN base station 504 and the UE 508 initial communicationsparameters are communicated from the NTN base station to the UE 508, forexample as part of RRC radio bearer establishment. An example of theseinitial communications parameters are:

-   -   Satellite        -   Satellite type/ID        -   orbit (almanacs and ephemerides)        -   attenuation due to atmospheric gasses        -   attenuation due to either ionospheric or tropospheric            scintillation        -   attenuation due to weather conditions (e.g. rain)        -   noise due to solar condition (e.g. solar storm)    -   Surrounding environment        -   attenuation due to penetration loss (if not line of site),            UE may use the geo-location database/indoor positioning.        -   multipath effect (interference with ground reflection), UE            may use the geo-location database and possible effect (on            the concrete ground, on the sea)        -   fading margin (e.g. indoor or outdoor)        -   mobility type (e.g. stationary, ship or airplane), UE may            measure the speed or altitude by GNSS or own inertia            sensors. Or the location server may have the type of UE and            indicate it UE.        -   interference due to man-made noise (e.g. urban area, close            to radar) and so on

As explained above, according to example embodiments, the controller 544of the UE 508 models a state of the radio communications channel betweenthe UE 508 to the NTN satellite 504 to adapt the communicationsparameters in accordance with a link adaptation procedure. As explainedthe UE receives the initial communications parameters as explainedabove, for example, from the RRC radio bearer establishment (for exampleassistance information of satellite orbit, propagation relatedattributes). The controller 544 of the UE 508 also uses internalparameters such as a current time/date and its current UE position and aprediction of a position of the NTN base station 504 (step S4 in FIG. 4), based, for example on an orbit of a satellite or the flight plan of adrone, depending on the nature of the NTN base station 504.

Based on it, UE predicts the path loss (step S6 of FIG. 4 ) and thenoise and interference (step S8 of FIG. 4 ) separately. According to themodel determined by the controller 544 of the UE 508, the UE calculatesan estimate of the signal to interference and noise ratio of signalsreceived at the NTN base station 504, which is applied to for example alookup table to determine a set of communications parameters fortransmitting data in accordance with a link adaptation procedure.

As will be appreciated from the above explanation, the controller 534 ofthe NTN base station 504 could also estimate the signal to interferenceand noise ratio of signals transmitted by the UE 508 and received at theNTN base station 504 to identify the communications parameters beingapplied by the UE 508.

According to one example embodiment, the model generated by the UE 504determines the path loss in step S4 of FIG. 4 using factors such as:

-   -   Distance between UE and a base station (basis of pathloss)    -   Atmospheric effects for electromagnetic waves such as        reflection, absorb.    -   UE use environments such as building penetration loss, clutter        type (e.g. urban, rural, sea)        In one example, the model applied by the UE 508 calculates the        path loss (PL) as follows:

PL=PL_(b)+PL_(g)+PL_(s)+PL_(e),

where PL is the total path loss in dB,

-   -   PL_(b) is the basic path (free space) loss in dB, calculated        based on the distance    -   PL_(g) is the attenuation due to atmospheric gasses in dB,        provided by assistance information    -   PL_(s) is the attenuation due to either ionospheric or        tropospheric scintillation in dB, by assistance information    -   PL_(e) is building entry loss in dB, which could be determined        by the geo-location database. The PLg and the PLs could be        provided by system information transmitted by the NTN base        station 504 if it holds a GIS database which incoporates these        parameters. The free space loss can be calculated by a formular        PL_(b)=(4πdf/c)². The model may also include a building        penetration, which can be sensed by the UE. In some examples,        the factors PL_(g) and PL_(s) could be communicated as part of        the initial parameters as a combined attenuation value to reduce        signalling.

Accordingly the UE can calculate the path loss as part of the model inaccordance with the following as represented in FIG. 4 :

-   -   1. The UE receives the initial parameters;    -   2. The UE calculates the estimated satellite position based on        the orbit calculation;    -   3. The UE calculates the distance between its own position and        the estimated satellite position at the time of its next        transmission;    -   4. The UE converts the distance to a path loss based on the        above formula.

As explained above, according to the example embodiment presented inFIG. 4 , in step S8 the model generated by the UE 508 calculates thesignal to interference and noise ratio using such factors as:

-   -   External disturbance such as solar storm, man-made noise    -   Use environments such as mobility speed, multi-path effects,        interference from other cell/other UEs.

According to one example, the model may receive as part of the initialparameters an indication of a current noise and interference powerdetected at the NTN base station 504 and then adjusts this initialindication in accordance with some error factor or time/distance varyingproperty for more accuracy based on feedback loop during thecommunication. For example the interference and noise (NI) may beassumed to be composed of the components:

NI=Ne(external noise)+Ni(internal noise)+No(un-orthogonal interferencefactor)

In the above equation:

-   -   NI is the total noise in dB, Ne is the external noise in dB such        as other that produced by other UE interference such as man-made        noise. According to one example, the NTN base station 504 could        measure the noise and interference as part of a received signal        strength indication (RSSI) when received signals are low as a        result of low traffic or during a dedicated time slot for        measurement. This value could be transmitted with the broadcast        system information from the NTN base station 504 to the UE 508.    -   Ni is the internal noise in dB such as a noise figure for a low        noise amplifier and feeder loss, which the NTN base station 504        could determine from an initial factory setting or a setup        measurement. Thermal noise (kTB) depends on the temperature and        so needs to be measured at the UE. This Ni value could be        provided by with the system information or as assistance        information as some other message exchange. In above, k is        Boltzmann's constant, T is absolute temperature, B is the NTN        base station transponder receiver bandwidth.    -   No is the interference in dB such as un-orthogonal factor or        multipath effect, which may use the historical value based on        geo-location. Perhaps, negligible for uplink

For simplification and reduction in signalling overhead, some noiseparameters could be merged into a consolidated value, which couldprovide an indication for a lookup table present in the UE 508.

Accordingly the UE can predict the noise and interference at thereceiver 532 in the NTN base station 504 as part of the model inaccordance with the following as represented by step S8 in FIG. 4 :

-   -   1. The UE receives initial information as part of the initial        communications parameters (step S1 or S24).    -   2. The UE calculates the estimated noise and interference based        on these communications parameters, which may include some        error. For example, as explained above these could be calculated        according to the above formula NI=Ne(external noise)+Ni        (internal noise)+No (unorthogonal interference factor) or, more        simply, a base station may send the RSSI to the UE, which the UE        may use as an approximate value.    -   3. The controller 544 of the UE 508 may be configured as part of        the model to accumulate a history of error detection results,        for example an indication of a number of errors can be made        based on a ratio of NACK/(ACK+NACK) from a base station received        from the NTN base station 504 as part of a Hybrid ARQ        communication scheme. It should be noted however that in some        example applications such as where the NTN base station is        located in a satellite a long round trip delay for transmission        be make HARQ unfeasible to use and so may be suspended.    -   4. If the number of detection errors is        -   a. higher than expected            -   i. the UE can increase the internal variables of                estimated noise/interference.        -   b. lower than expected            -   i. the UE can decrease the internal variables of                estimated noise/interference.        -   c. almost equal to that expected            -   i. (current model looks accurate)                -   UE keeps the current value of the internal variables                    of estimated noise/interference.    -   5. The UE stores the internal variables of estimated        noise/interference for its next transmission.    -   6. Optionally, at the end of a session or during a session, the        UE may send a compensated value of noise and interference (NI)        to the NTN base station 504. The NTN base station 504 could use        it for calibration of its own initial parameters.    -   7. If the UE faces a still higher error rate after the UE has        changed the internal variables of estimated noise/interference        or the UE can receive neither ACK nor NACK, then the UE        deactivates the persistent scheduling or reverts to radio link        failure (RLF) procedure as represented as step S28 and messages        M6, M8 explained above.

As explained, the UE obtains the parameters for the calculation of thenoise and interference from one or more of:

-   -   RRC dedicated signalling, such as for example semi-persistence        signalling configuration;    -   System information, such as System information Blocks broadcast        by the NTN base station;    -   Assistance information transmitted by a satellite such as        assisted GPS, assistance information communication like        Internet/Wifi, SIB by cellular network etc.    -   Geo-location database, which may be pre-configuration at UE or        downloaded via Internet.

As indicated above, in some examples the controller 534 in the NTN basestation 504 may also generate the same model to mimic the operation ofthe controller 544 in the UE 508 to generate an estimate of thecommunications parameters used to transmit the data from the UE 508 inaccordance with the link adaptation procedure. This is because currentversions of 3GPP standards such as release-15 do not provide forcommunications resources to transmit uplink control information (UCI) onphysical uplink channels such as a PUCCH/PUSCH to send the selected linkadaptation parameters to the NTN base station 504. For this reason theNTN base station 504 is configured to arrange for the receiver 532 todetect the radio signals transmitted from the UE 508 and to decode theuplink data without an explicit indication of the communicationsparameters used to transmit the uplink data.

An example link adaptation procedure adapts for example the transmissionpower to ensure that a target signal to noise and interference ration(SNIR) is achieved whilst maintaining others of the communicationsparameters such as modulation index and error correction coding rate thesame. For this example, the NTN base station 504 does not require anyadaptation of the other communications parameters to detect and estimatethe uplink data with respect to these communications parameters (otherthan the communications parameters of transmission power) established atthe start of the session for example with the RRC radio bearerconfiguration. A restriction on the application of this link adaptationtechnique may be that the transmitter does not have enough powerheadroom for increasing the transmission power. However increasing thetransmission power beyond a certain limit may not increase an integrityof the communicated data beyond a certain limit and therefore a rate ofdata transmission above a certain transmission power. As such whenhigher than available transmission powers are required, it may beappropriate to adapt other communications parameters such as themodulation index and error correction encoding rate.

As indicated above there are two techniques for detecting radio signalstransmitted by a UE according to example embodiments in which linkadaptation is applied by the UE based on modelling the channel state asexplained above. The first technique is to configure the controller 544to model the channel state to reflect the model performed at the UE. Thesecond is to perform a blind detection of the radio signals and togenerate an estimate of the data carried by the radio signals using allpossible permutations of the communications parameters other than thetransmission power.

The first technique assumes that both the transmitter (UE) and receiver(NTN base station) has identical calculation models for estimating thechannel state. Instead of power control, the UE applies the estimatedchannel state to select a suitable modulation and coding (MCS) and/ortransport block size with the same output of the model.

The challenge with this first technique is for the base station todetect and to decode the data without knowing the transmission bufferstatus or a block size used by the transmitter at the receiver. In oneembodiment, a static block size is used so that the receiver can assumethe same data size for next transmission. That is to say, thetransmitter in the UE is configured to use the same transport block sizeindicated as part of the initial parameters and is either fixed for theduration of the communications session or varied by a predeterminedamount for conditions that can be identified by each of the transmitter(UE) and the receiver (NTN base station). For example a transport blocksize can be mapped on to a certain selected modulation scheme and errorcorrection encoding rate. Optionally, in order to provide moreflexibility for the grant of communications resources, the UE may sendthe buffer status and/or power headroom to the NTN base station.

As mentioned above, the second detection technique applied at thereceiver (NTN base station) is blind detection in which, for example,the receiver tries all combinations of the communications parameters(other than transmission power) to detect and to decode the uplink data.There are various ways of blind detection at the receiver such as energydetection, or CRC detection. In one example embodiment, the linkadaptation procedure restricts a number of combinations of thecommunications parameters (other than transmission power) at thetransmitter (UE) so that the number of possible combinations of thecommunications parameters which are needed to perform the blinddetection can also be reduced. For example, the number of possiblecombinations for communications parameters for link adaptation can bereduced to for example to two or three possible combinations ofparameters, for example, by fixing a modulation scheme (constellationsize) with limited transport block size combination. Furthermore anincrease of the CRC size can be used, for example 24 bits or more inorder to avoid misdetection.

As a hybrid method a link adaptation procedure could switch betweendifferent techniques, such as power adaptation only until a maximumpower has been reached in which case both the transmitter and thereceiver switch to a different and fixed modulation and coding rate andthen adapt the transmission power again until the maximum transmissionpower is reached.

According to some embodiments either the transmitter (UE) or thereceiver (NTN base station) can detect conditions which abort the linkadaptation procedure and so fall back to a conservative schedulingposition. For example, if the controller detects using the model of thechannel state, that the channel state is not suitable for linkadaptation then the transmitter (UE) is configured to abort thepredictive scheduling and fall back to conservative scheduling and use alow modulation scheme, low channel coding rate and a small transportblock size in line with a largest path loss assumption. In anotherexample, if the model is in error and is determined not to match theactual channel state, the UE may send a trigger to abort link adaptationwith explicit signalling, for example by deactivation of MAC CE. Inanother example, the NTN base station may understand that the UE hasaborted link adaptation because the receiver detects and decodes thatdata using default communications parameters or an explicit report isreceived from the UE, if for example there is only a small amount of epower headroom available.

Embodiments of the present technique can provide an arrangement in whicha UE is able to perform link adaptation without receiving channel stateinformation from the NTN base station. In one example the UE cancommunicate uplink data whilst economically using transmission power, byreducing the transmission power to a minimum required for a givenchannel state and modulation and coding scheme. Furthermore a moreefficient use of communications resources can be achieved by thewireless communications network through a reduced signalling overheadand an improved data rate by reducing a number of retransmissions at theNTN base station.

From UE point of view, the UE is able to select the optimal linkadaptation parameters. UE transmissions can enjoy a low error ratewithout excessive transmission power.

From base station/network point of view, the network reduces the numberof retransmissions or avoid cell throughput decrease. The network canenjoy efficient radio resource usage and reduction of signallingoverhead in addition to user throughput increase.

It will be appreciated that while the present disclosure has in somerespects focused on implementations in an LTE-based and/or 5G networkfor the sake of providing specific examples, the same principles can beapplied to other wireless telecommunications systems. Thus, even thoughthe terminology used herein is generally the same or similar to that ofthe LTE and 5G standards, the teachings are not limited to the presentversions of LTE and 5G and could apply equally to any appropriatearrangement not based on LTE or 5G and/or compliant with any otherfuture version of an LTE, 5G or other standard.

It may be noted various example approaches discussed herein may rely oninformation which is predetermined/predefined in the sense of beingknown by both the base station and the terminal device.

It will be appreciated such predetermined/predefined information may ingeneral be established, for example, by definition in an operatingstandard for the wireless telecommunication system, or in previouslyexchanged signalling between the base station and terminal devices, forexample in system information signalling, or in association with radioresource control setup signalling. That is to say, the specific mannerin which the relevant predefined information is established and sharedbetween the various elements of the wireless telecommunications systemis not of primary significance to the principles of operation describedherein.

It may further be noted various example approaches discussed herein relyon information which is exchanged/communicated between various elementsof the wireless telecommunications system and it will be appreciatedsuch communications may in general be made in accordance withconventional techniques, for example in terms of specific signallingprotocols and the type of communication channel used, unless the contextdemands otherwise. That is to say, the specific manner in which therelevant information is exchanged between the various elements of thewireless telecommunications system is not of primary significance to theprinciples of operation described herein.

Further particular and preferred aspects of the present invention areset out in the accompanying independent and dependent claims. It will beappreciated that features of the dependent claims may be combined withfeatures of the independent claims in combinations other than thoseexplicitly set out in the claims.

Thus, the foregoing discussion discloses and describes merely exemplaryembodiments of the present invention. As will be understood by thoseskilled in the art, the present invention may be embodied in otherspecific forms without departing from the spirit or essentialcharacteristics thereof. Accordingly, the disclosure of the presentinvention is intended to be illustrative, but not limiting of the scopeof the invention, as well as other claims. The disclosure, including anyreadily discernible variants of the teachings herein, define, in part,the scope of the foregoing claim terminology such that no inventivesubject matter is dedicated to the public.

Respective features of the present disclosure are defined by thefollowing numbered paragraphs:

Paragraph 1. A method of transmitting data by a terminal device via awireless communications system, the method comprising the terminaldevice

-   -   receiving an indication of an initial value of a set of one or        more communications parameters for transmitting radio signals        carrying the data,    -   modelling a state of a communications channel from the terminal        device to a receiver of the radio signals,    -   using a link adaptation procedure to select a revised value of        the set of the one or more communications parameters with        respect to the initial value of the set of the one or more        communications parameters for the modelled channel state, and    -   adapting the value of the set of the one or more communications        parameters according to the revised value, and    -   transmitting radio signals representing the data using the        adapted set of the one or more communications parameters.

Paragraph 2. A method according to Paragraph 1, comprising

-   -   determining by the terminal device a distance between the        terminal device and a receiver of the radio signals, wherein the        modelling the state of the communications channel includes    -   estimating a path loss between the terminal device and the        receiver, and    -   estimating a power with which the transmitted radio signals are        received by the receiver based on a power with which the radio        signals are transmitted and the estimated path loss, and the        link adaptation procedure includes    -   selecting the revised value of the set of the one or more        communications parameters with respect to the initial value        using the estimated received signal power.

Paragraph 3. A method according to paragraph 2, wherein the terminaldevice includes a location detector for generating an estimate of alocation of the terminal device and the determining, by the terminaldevice, the distance between the terminal device and the receiver of theradio signals includes

-   -   receiving an indication of a location of the receiver of the        transmitted radio signals when a communication session for        transmitting the data starts, information indicating a path of        travel of the receiver and a speed of the receiver, and when        selecting the revised value of the one or more communications        parameters according to the link adaptation procedure,    -   estimating, at a time of modelling the channel state, a location        of the receiver based on the location of the receiver when the        communication session started, the path of travel of the        receiver, the speed of the receiver and an elapsed time from the        start of the communications session and the time of modelling        the channel state    -   estimating a location of the terminal device using the location        detector,    -   estimating the distance between the terminal device and the        receiver based on the estimated location of the terminal device        and the estimated location of the receiver.

Paragraph 4. A method according to paragraph 3, wherein the indicationof the location of the receiver of the transmitted radio signals whenthe communication session starts, the information indicating the path oftravel of the receiver and the speed of the receiver are received by theterminal device with the initial value of the set of the one or morecommunications parameters.

Paragraph 5. A method according to any of paragraphs 2, 3 or 4, whereinthe path loss is estimated using an indication of at least one of a freespace loss, attenuation due to atmospheric gasses, attenuation due toeither ionospheric or tropospheric scintillation and building entryloss.

Paragraph 6. A method according to any of paragraphs 1 to 5, wherein themodelling the channel state includes generating an estimate of a signalto interference and noise ratio for the received radio signals at thereceiver from the estimated power with which the transmitted radiosignals are received by the receiver with respect to an estimate ofnoise power and an estimate of interference power.

Paragraph 7. A method according to paragraph 6, wherein the estimate ofthe noise power and the estimate of the interference power is receivedby the communications terminal with the indication of the initial valueof the set of the one or more communications parameters.

Paragraph 8. A method according to paragraph 6 or 7, wherein the one ormore communications parameters of the set includes a transmission powerwith which the radio signals are transmitted and the link adaptationincludes adjusting the transmission power with respect to the estimatedsignal to interference and noise ratio for the received radio signals atthe receiver.

Paragraph 9. A method according to paragraph 6 or 7, wherein the one ormore communications parameters of the set includes a size of amodulation scheme which is used to modulate one or more carrier signalsof the radio signals with the data to be transmitted, and an errorcorrection encoding rate.

Paragraph 10. A method according to paragraph 10, wherein the linkadaptation includes selecting from a limited set of combinations of thesize of the modulation scheme and the error correction encoding rate.

Paragraph 11. A method according to any of paragraphs 1 to 10, whereinreceiver forms part of a non-terrestrial network access node, theterminal device and the non-terrestrial network access node forming partof the wireless communications system

Paragraph 12. A terminal device for transmitting data via a wirelesscommunications system, the terminal device comprising

-   -   transmitter circuitry configured to transmit radio signals        representing the data via a wireless access interface to a        receiver,    -   receiver circuitry configured to receive radio signals        transmitted from the wireless communications system, and    -   controller circuitry configured to control the transmitter and        the receiver to transmit and receive the radio signals, wherein        the controller circuitry is configured    -   to receive an indication of an initial value of a set of one or        more communications parameters for transmitting radio signals        carrying the data,    -   to model a state of a communications channel from the terminal        device to a receiver of the radio signals,    -   to use a link adaptation procedure to select a revised value of        the set of the one or more communications parameters with        respect to the initial value of the set of the one or more        communications parameters for the modelled channel state,    -   to adapt the value of the set of the one or more communications        parameters according to the revised value, and    -   to transmit radio signals representing the data using the set of        the one or more communications parameters.

Paragraph 13. A method of receiving uplink data from a terminal deviceat network infrastructure equipment comprising a non-terrestrial networkaccess node in a wireless telecommunications system comprising thenetwork infrastructure equipment and a terminal device, the methodcomprising

-   -   transmitting an indication of an initial value of a set of one        or more communications parameters for the terminal device to        transmit radio signals carrying uplink data to be received, and    -   receiving the uplink data transmitted with a revised value of        the set of the one or more communications parameters which have        been adapted with respect to the initial value of the set of the        one or more communications parameters in accordance with a link        adaptation procedure based on an estimate of a state of a        communications channel between the terminal device the receiver        circuitry estimated using a model of the channel state generated        by the terminal device.

Paragraph 14. A method according to paragraph 13, comprising

-   -   generating a model of the channel state to mimic the model of        the channel state generated by the terminal device,    -   generating an estimate of the revised value of the set of the        one or more communications parameters which have been adapted        with respect to the initial value of the set of the one or more        communications parameters in accordance with the link adaptation        procedure based on the model of the state channel performed at        the receiver, and    -   controlling the receiver to detect the radio signals and to        estimate the uplink data in accordance with the estimate of the        revised value of the set of the one or more communications        parameters.

Paragraph 15. A method according to paragraph 13, wherein thecontrolling the receiver to detect the radio signals and to estimate theuplink data includes

-   -   detecting the radio signals and estimating the uplink data using        a blind detection technique by attempting possible values of the        set of the one or more link adaptation parameters until the        uplink data is determined to have been correctly decoded.

Paragraph 16. Network infrastructure equipment comprising anon-terrestrial network access node in a wireless telecommunicationssystem comprising the network infrastructure equipment and a terminaldevice, the network infrastructure equipment comprising

-   -   transmitter circuitry configured to transmit radio signals        representing data via a wireless access interface,    -   receiver circuitry configured to receive radio signals via the        wireless access interface, and controller circuitry configured        to control the transmitter and the receiver to transmit and        receive the radio signals, wherein the controller is configured        control the transmitter    -   to transmit an indication of an initial value of a set of one or        more communications parameters for the terminal device to        transmit radio signals carrying uplink data to be received, and        to control the receiver    -   to receive the uplink data transmitted with a revised value of        the set of the one or more communications parameters which have        been adapted with respect to the initial value of the set of the        one or more communications parameters in accordance with a link        adaptation procedure based on an estimate of a state of a        communications channel between the terminal device the receiver        circuitry estimated using a model of the channel state generated        by the terminal device.

Paragraph 17. Network infrastructure equipment according to paragraph16, wherein the controller is configured

-   -   to generate a model of the channel state to mimic the model of        the channel state generated by the terminal device,    -   to generate an estimate of the revised value of the set of the        one or more communications parameters which have been adapted        with respect to the initial value of the set of the one or more        communications parameters in accordance with the link adaptation        procedure based on the model of the state channel performed at        the receiver, and    -   to control the receiver to detect the radio signals and to        estimate the uplink data in accordance with the estimate of the        revised value of the set of the one or more communications        parameters.

Paragraph 18. Network infrastructure equipment according to paragraph16, wherein the controller is configured to control the receiver todetect the radio signals and to estimate the uplink data using a blinddetection technique attempting possible values of the set of the one ormore link adaptation parameters until the uplink data is determined tohave been correctly decoded.

Paragraph 19. Circuitry for transmitting data via a wirelesscommunications system, the circuitry comprising

-   -   transmitter circuitry configured to transmit radio signals        representing the data via a wireless access interface to a        receiver,    -   receiver circuitry configured to receive radio signals        transmitted from the wireless communications system, and    -   controller circuitry configured to control the transmitter and        the receiver to transmit and receive the radio signals, wherein        the controller circuitry is configured    -   to receive an indication of an initial value of a set of one or        more communications parameters for transmitting radio signals        carrying the data,    -   to model a state of a communications channel from the terminal        device to a receiver of the radio signals,    -   to use a link adaptation procedure to select a revised value of        the set of the one or more communications parameters with        respect to the initial value of the set of the one or more        communications parameters for the modelled channel state,    -   to adapt the value of the set of the one or more communications        parameters according to the revised value, and    -   to transmit radio signals representing the data using the set of        the one or more communications parameters.

Paragraph 20. Circuitry comprising

-   -   transmitter circuitry configured to transmit radio signals        representing data via a wireless access interface,    -   receiver circuitry configured to receive radio signals via the        wireless access interface, and controller circuitry configured        to control the transmitter and the receiver to transmit and        receive the radio signals, wherein the controller is configured        control the transmitter    -   to transmit an indication of an initial value of a set of one or        more communications parameters for a terminal device to transmit        radio signals carrying uplink data to be received, and to        control the receiver    -   to receive the uplink data transmitted with a revised value of        the set of the one or more communications parameters which have        been adapted with respect to the initial value of the set of the        one or more communications parameters in accordance with a link        adaptation procedure based on an estimate of a state of a        communications channel between the terminal device the receiver        circuitry estimated using a model of the channel state generated        by the terminal device.

REFERENCES

-   [1] 3GPP TR 38.811 “Study on New Radio (NR) to support non    terrestrial networks (Release 15)”, December 2017-   [2] Holma H. and Toskala A, “LTE for UMTS OFDMA and SC-FDMA based    radio access”, John Wiley and Sons, 2009

1. A method of transmitting data by a terminal device via a wirelesscommunications system, the method comprising the terminal devicereceiving an indication of an initial value of a set of one or morecommunications parameters for transmitting radio signals carrying thedata, modelling a state of a communications channel from the terminaldevice to a receiver of the radio signals, using a link adaptationprocedure to select a revised value of the set of the one or morecommunications parameters with respect to the initial value of the setof the one or more communications parameters for the modelled channelstate, and adapting the value of the set of the one or morecommunications parameters according to the revised value, andtransmitting radio signals representing the data using the adapted setof the one or more communications parameters.